1. Field
This application relates generally to processes for rendering shadows in computer generated imagery (CGI) animation scenes and, more specifically, to computer systems and processes for integrating two-dimensional (2D) shadow characters into three-dimensional (3D) CGI scenes.
2. Related Art
CGI animation tools are available for generating naturally-cast shadows (or true shadows) in 3D animation scenes. Naturally-cast shadows may be based on various light sources in a 3D CGI environment. For example, a primary light source may generate naturally-cast shadows that appear highly realistic and uniform for the various illuminated objects in the scene. In an outdoor environment, for example, the primary light source may correspond to the sun, which may cause naturally-cast shadows with the appropriate size, shape, angles, interference, and the like based on the object geometry between the sun and the various surfaces in the environment. Moreover, multiple light sources in an environment may combine to soften shadows, cast additional shadows, and generally provide additional realism to the animated scene.
For some storylines, however, naturally-cast shadows may be insufficient. For example, a storyline may include a shadow character that may move, talk, or otherwise perform independently from a 3D modeled character. Such a shadow character may be made to appear as a featured element—an animated character itself—in a scene as opposed to a naturally-cast shadow that may add realism as part of the background. For example, the naturally-cast shadow of a 3D modeled character may come alive and deviate from the naturally-cast form that would typically be produced by scene lighting (e.g., talking on its own, gesturing on its own, etc.).
Incorporating 2D shadow characters into a 3D CGI scene, however, can be geometrically challenging, time consuming, and tedious, among other things. Typically, animators may draw such a shadow character into each frame by hand. Drawing such complex shapes with the appropriate curvature, distortion, angle, interference, and the like can be very time consuming, and it may lead artists to spend considerable time focusing on the technical details of how the shadow falls in the scene compared to the basic performance of the shadow character. In other words, a shadow character's movements and features—that may be important to the storyline—may suffer due to the complexity of getting the shadow to accurately interact with and conform to objects in an environment. Moreover, with the tedious task of drawing the shadow character frame after frame, human error can cause registration problems, wobbly lines, and other artifacts that may cause the drawn shadow character to look fake and unnatural. Such errors and artifacts may end up distracting from the storyline and weakening the role of the shadow character.
In addition, manually drawing a shadow character into each frame with precise contouring can make any later changes to a scene layout prohibitively expensive and time consuming. For example, as film production progresses, it may become desirable to modify a scene by moving objects, changing characters, adjusting lighting, or adjusting various scene elements. However, doing so may require redrawing a shadow character in each frame of the modified environment—with accurate contouring—to accurately depict changes. Such a tedious frame-by-frame process is a stark contrast to the powerful CGI tools available to rapidly implement changes and re-render scenes as desired.
Thus, systems and processes for integrating 2D drawn shadow characters in 3D CGI scenes with realistic contouring on 3D objects are desired.